high altitude medicine - akutne.cz · 2016-11-09 · normal physiology veronika m. bartova: high...

High Altitude Medicine

Veronika M. Bartova, M.D.

1Veronika M. Bartova: High Altitude Medicine, November 2016

About me

• Studied at the Medical Faculty, Charles

University in Prague

• Clinical practice for 17 years as an internist –

nephrologist, head of dialysis unit in Prague

• Participated in a number of expeditions to peaks higher

than 6 000 m (including one 8 000 m peak) as an

expedition doctor

• Currently in a global medical role at GlaxoSmithKline

(Pharmaceutical company)


Medical advice


Recommendations

Before departure for a trek or an expedition:

• routine medical check up (blood pressure,

ECG, basic biochemistry - namely blood

glucose, cholesterol, blood count);

• dentist check up;

• gynaecology check up for women.


Basic vaccination

• typhoid

• rabies

• cholera

7

• hepatitis A

• hepatitis B

• tetanus

Veronika M. Bartova: High Altitude Medicine, November 2016

Other vaccination

• Requirement depends on the approach route to

the final trekking or climbing destination (rain

forrest, rural area etc.).

• Consult a vaccination center for an advice what

other vaccination is mandatory and/or

recommended for the specific destination.

• Vaccination for the prevention of yellow fever,

meningococcal diseases, japanese encephalitis

as well as prevention against malaria may be

considered.


Take care

• Radial keratotomy (myopia correction) can lead

to refractive changes at altitude from minor

discomfort to severe disability.

• There is an increased risk of thrombotic events

at high altitude.

– Oral contraceptives make this risk even higher.

– Tight fitting socks (elastic bands) reduce blood

circulation and can also lead to thrombophlebitis.


Normal physiology


Definitions

• High altitude 1 500 – 3 500 m

• Very high altitude 3 500 – 5 500 m

• Extreme altitude above 5 500 m

• Zone of tolerance – individual, changes with acclimatisation.

• When above 3000 m, it is recommended to ascend 300 to 500 m per day and have a rest day for acclimatisation every gained 1000 m (or every 3 days).



High altitude

Normal reaction to altitude

• hyperventilation during exertion

• shortness of breath during exertion, resolving

rapidly at rest

• changed breathing pattern at night

(Cheyne-Stokes)

• increased urine output

• awakening at night

• weird dreams


Altitude and atmospheric pressure

• The amount of oxygen (O2) in the air at the altitude of 5 500 m is 50 % of that at sea level. At the altitude of 8848 m (Mt Everest) it is only 30 %.

• The atmospheric pressue at a given sea level is higher around the equator and is higher in the summer than in the winter.


Pulse & PaO2

• Partial pressure of arterial oxygen at 4 200 m: 80 – 86 % normal acclimatized,

50 – 60 % with HAPE.When giving O2 saturate the arterial blood to 99 – 100 %.

• Pulse oxymeter – simple, light and easy device for monitoring individual acclimatisation.Pulse at altitude increases by 20 beats per min at awakening without acclimatization, returns to normal when acclimatized.

Appropriate O2 saturation at the cost of extremely increased pulse rate is a sign of insufficient acclimatisation.

Very low O2 saturation and an extremely increased pulse rate is a sign of high altitude disease.


Pulse oxymeter


Altitude

• Human habitation ends at the altitude of 5 400 m.

• It is possible to stay at altitude over 6 000 m for weeks or months, but organism starts to deteriorate.

• Aim to acclimatize up to 6 500 m. Above that, it is just tolerance, no further acclimatization is possible.

• At high altitude there is an increased risk of bacterial, not viral infection.

– Active immunity and B cell function is normal.

– T cell function is impaired.


Nutrition & hydration

• It is essential to keep good hydration at altitude.

– Air at high altitude is dry, the fluid intake must be

increased compared to low altitude.

– If no unusual fluid loss - intake should be at least

3 litres / 24 hrs up to 6 000 m.

– Above 6 000 m - fluid intake over 3 litres / 24 hrs.

– Simple test – pale yellow urine colour.

• Diet should have > 70 % of energy from

carbohydrates (pasta, rice, potatoes…).


High altitude medical

disorders & diseases


Acute mountain sickness (AMS)

• Pathophysiology is not fully understood.

• Symptoms from brain swelling due to hypoxic stress.

• AMS = headache + 1 of the following symptoms:– loss of apetite, nausea, vomiting;

– fatigue and/or weakness;

– dizziness and/or lightheadedness;

– difficulty sleeping;

– dtaggering gait (unable to walk in straight line but normal finger to nose test);

– Confusion.

(Spontaneously resolving headache after sufficient fluid intake is not AMS.)


25

High altitude hypoxemia

Sympathetic activity

increased

BrainLungs

Pulmonary blood

volume increased Pulmonary venous

constriction

Endothelial

activation ?

Capillary permeability

increased ?

Uneven

vasoconstriction

Regional

overperfusion

Capillary pressure

increased

Capillary leakageHigh altitude

pulmonary oedema

Pulmonary blood

volume increased

Pulmonary artery

pressure increased

Vasodilation

Cerebral blood

volume

increased

Cerebral

blood flow

increased

Capillary pressure

increased

Urinary Na excretion

decrease, aldosterone

and arginine vasopressin

increase – Na retention

and extracelular fluid

increase Vasogenic

oedema

High altitude

brain oedema

Intracranial pressure

increased

Retinal haemorrhage

Exaggerated

hypoxemia

Pathophysiology of AMS

Veronika M. Bartova: High Altitude Medicine, November 2016

Altitude disorders & diseases

• dehydration & oedema

• diarrhoea

• cough; CO poisoning

• snow blindness

• frostbite

• hypothermia

• high altitude pulmonary edema (HAPE)

• high altitude cerebral edema (HACE)


Dehydration & oedema

• Dehydration increases the risk of headache &thrombotic complications.

• There is an extreme loss of fluid during physical activity at high altitude (especially in sunny weather).

• Peripheral oedema (face – puffy eyes, swollen feet) in absence of other symptoms of AMS can be treated with acetazolamide (Diamox) or other mild diuretic.


Diarrhoea

• Diarrhoe is not always of infectious aetiology –

do not treat with ATB before trying other means

(ATB can make it worse by killing the normal

intestinal bacteria).

• Possible causes: dietary, stress, allergy,

medication).

• Sufficient fluid and mineral intake – use

electrolyte supplements (mineral drinks).


Cough; CO poisoning

• Dry air leads to dry irritative cough (so-called Khumbu cough). Note – do not overlook beginning HAPE.

• Carefull when cooking inside tents at high altitude – let sufficient fresh air in to avoid CO poisoning.

• When cooking inside tent, move all inflamable materials far from gas stove.


Snow blindness

• UV keratitis – damage caused by the strong ultraviolet light to the eye cornea with reactive conjunctival inflammation.

• It is very painfull and causes temporary blindness.

• Usually resolves in 2 to 5 days; if serious, can leave permanent damage.

• Prevention – sunglasses with category 4 filter.


Frostbite

• Local damage caused by low temperature

• Enhanced by dehydration

• Prevention:

– dry clothes & boots.

– Never ignore numbness (it may happen to be the last sensation you´ve ever felt).

– Use thin gloves for cooking, fotography…

• Never rub frostbitten area directly, defrost only when further treatment is possible.


Hypothermia

• Overall damage caused by low temperature

– Normal body temperature is 37 oC.

– Decrease of body temperature below 37 oC leads

to shiverring.

– With further decrease below 36,5 to 35 oC shivering

stops, feeling of dizziness and disorientation appears,

pulse is weak and slow, illusion of warmth follows,

then the heart stops.

• Risk increases in strong wind, with hunger,

dehydration, exhaustion.


Fatigue

• Increases the risk of possible

– complications (frostbite, dehydration, hypothermia);

– mistakes (falling into crevasses, stepping into the void);

– bad judgement (distance & time estimation).

• Fatigue cannot be always avoided, but should always be remembered as a risk factor and precautions taken.


High Altitude Pulmonary Edema

(HAPE)

• HAPE is caused by fluid retention in the lung interstitial tissue, progresses into fluid in the lung alveoli.– Signs & symptoms: fatigue, breathlesness at rest, cough,

pink sputum, fast and shallow breathing, blue lips and fingertips, gurgling sounds when breathing.

• Never take HAPE for pneumonia, never treat with ATB at high altitude, always descend, then treat if needed.

• May culminate the 1st or 2nd night after ascent! In case of any signs descend as fast & as low as possible (500 to 1 000 m lower).

• HAPE leads to extremely low PaO2, may be equal to rapid ascent & lead to progressive HACE.


High Altitude Cerebral Edema

(HACE)• Brain swelling due to hypoxia, alteration of all brain

functions.

– Signs & symptoms: change of mentation & ability to think, agitation or lethargy, loss of coordination, ataxia (walking straight line is altered, touching the nose tip with closed eyes is not).

• Immediately descend as fast and as low as possible (at least 500 – 1 000 m), never wait till the morning at the same altitude – it may be too late in the morning!

• Treatment will help the sick person survive, but cannot match the positive effect of descent. Syptoms usually recede spontaneously at lower altitude.


Rescue

• Do not underestimate the risks even when you

go “just” trekking.

• Always have an option to call help (satelite

phone, walkie-talkie).

• Be sure to have correct rescue phone numbers.

• Do not hesitate to call for help – better rather

early than too late.

• Have basic treatment ready before help arrives

(oxygen, medication, Gamow bag).


Symptoms and long term effects

of high altitude exposure

• Transient disorders of motoric and sensory functions

have been described at high altitude including

transient congitive disorders and impaired memory.

• Neither long-term brain impairment nor disorder of

normal intelectual funcions following uneventfull (even

repeated) ascents to very high and extreme altitude

have been confirmed.

• In case of HACE (brain oedema) microhaemorrhage

has been identified by magnectic resonance imaging.

The laesions may persist up to several years.


Golden rules

• It is OK to get high altitude sickness. It is not OK

to die from it.

• Acetazolamide (Diamox) is not recommended as

a routine drug before any ascent!!!

• Any illness at altitude is altitude sickness unless

proven otherwise after descent.

• Never ascend with symptoms of AMS.

• If AMS is getting worse, descend at once. Do not

wait till the morning.

• Never leave someone with AMS alone.


Case studies

HACE – Biafo

Female 39 years, headache from the altitude of 3 000 m, improving at rest, slow ascent up to 4 150 m, where she loses coordination, feels extremely weak. Rescue hellicopter called at noon.

Treatment with Diamox & Hydrocortison started in camp at 4 pm. On treatment overnight, hellicopter cannot fly due to bad weather in Skardu. From morning unconscious, i.v. infusion, bradycardia treated by noradrenalin.

Hellicopter arrived at 2 pm, she left with the last available infusion. She received O2 on the way, was dismissed from hospital after 24 hrs without complications.


Case studies

HACE – Spantik

Female 42 years, descending from C2 to C1 accompanied by another climber. Unable to continue due to „fatigue“ decided to stay between camps.

Her partner left her alone and descended to C1 to bring help, which he had called by walkie-talkie. Two climbers returned to the place where she stayed three hours later and found her lying between 2 crevasses.

She was lying on the snow unconscious, no contact was possible. Then her heart stopped. Not even CPR brought her back to life.

Her body was burried in a crevasse at 5 431 m.


Medical kit


Personal medical kit

• Usual medication taken for any disorder,

antihistamines, aspirin, band aid, elastic

bandage, pain killers, paracetamol, water

purifying tbl.

• Multivitamin and mineral tablets and/or

drinks are recommended.


Expedition medical kit

• Tablets: antipyretics, analgetics, diarrhoea treatment, treatment for HAPE & HACE

• Antiinfectives: ATB, antivirotics, antiprotozoal (amoeba)

• Injections & infusions: corticosteroids, antithrombotics, analgetics, fluid replacement, treatment for HAPE & HACE

• Eye drops & ointments: antiinfectives, corticosteroids, analgetics

• Ointments & powder: antiinfectives, antimycotics, analgetics, antithrombotics, antiflogistics

• Varia: corticosteroid inhaler, antiemetics, desinfection

• Instruments, sutures, dressings: small surgical kit, syringes, needles, splints, infusion sets

• Oxygen as rescue treatment; Gamow bag


Literature1. Michael Knauth et al: High altitude climbers at risk for brain bleeds, Radiol

Soc of North America 2012, abstract SSM13-06

2. Kristina Fiore: Climbers Face Lasting Effects if Brain Swells, MedPage

Today, November 2012

3. Helen Albert: Brain effects of high altitude sickness retained long term,

Medwire News, November 2012

4. R. Douglas Fields: Into thin air: Mountain Climbing Kills Brain Cells,

Scientific American, April 2008

5. Peter H. Hackett, Robert C. Roach: High Altitude Illness, N Engl J Med,

July 2001

6. Andrew J. Pollard, David R. Murdoch: The High Altitude Medicine

Handbook, Book Faith India,1998

7. Mark D. Harris et al: High Altitude Medicine, American Family Physician,

April 1998

Illustration photos by Veronika M. Bartova, personal archive


high altitude medicine - akutne.cz · 2016-11-09 · normal physiology veronika m. bartova: high...

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